Okay I will preface this by saying that I have chopped the stlying about, added a couple of divs and spans and have probably by all rights dug my own hole.
That having been said, I've never come across this issue before so I was hoping that someone else had and might know what it is. When browsing the forum with IE I have an issue where comments sometimes don't show, usually the most recent comment. If I scroll the window, or highlight the text it will appear.